Process of recovering rubber from rubber waste.



ll N TED STATES PATENT OFFICE.

WILLIAM A. KONEMAN, F oHIo eo, ILLINOIS. PROCESS OF RECOVERING RUBBER FROM RUBBER wAsTB.

/ Nto. 823,053. Specification of Letters Patent. Patented June 12, 1906.

Application filed March 6, 1905. Renewed October 9, 1905. Serial No. 282,019.

To all y concern: servative ingredient, and by renderingin- Be it known-that I, WILLIAM A. KGNE- soluble and precipitating out of the rubber MAN, a citizen of the United States, residin all, or practically all, foreign matter in soluat Chicago, in. the countyof Cook and State ble form adhering thereto. 60

.of Illinois, have invented a new and useful The procedure, as hitherto practiced, of

Process of Recoverin .Rubber from Rubber recovering rubber from vulcanized-rubber Waste, of Which'the ollowing is a specificawaste and involvin the boiling of the matetlon. rial-either in an acid or an alkali solution re- My invention relates toan improvement on q uiresilie continuance of the boiling opera- 65 t e known processes of recovering rubber tion for a period offrom ten to twenty-four from cast-ofi' vulcanized rubber articles hours under a temperature of from 320 to which involve separation of the fibrous ma- 340" Fahrenheit to efi ect thorough removal terial from the rubber and devulcanization of the fiber and the necessary degree of deof the latter by boiling the material in the vulcanization of the rubber, a furtherre- 7o Ipresence of chemicals acting to dissolve the uirement being thatof agitating or stirring ber and to remove the sulfur or sulfur comt e mass during the entire time of treatment. pounds and washing the product to cleanse My invention involves the use of a chemical it of the chemicals, particles of fiber, and solution which enables the same results to be other impurities. As the art involving the accomplished underthe comparatively low 75 2o procedure thus generally outlined is now temperature of about 220 Fahrenheit in an 4 commonly practiced the rubber recovered by open'vessel within a period of about an hour practicing It is deficient instrength and elasand without agitation, and it reduce disticity and-is rarel entirely devoid of fiber, integration of heavy cotton fi er within a and goods manu actured from it tend to period of about five minutesmri'l his solution 80 2 5 harden and otherwise deteriorate rapidly. IS a weak solution of mineral acid containing This inherent weakness and inferior degree from five to ten per cent. of the acid with the I of elasticity of the reclaimed rubber are addition of an amount of commonsalt-(chlocaused, as I have discovered, b itsprorid of sodium) or other simple chlorid, such longed contact with the chemica s and the as calcium chlorid, in a proportionestimated'85 high temperature to which it is subjectedin as e ualing in weight about one-third that of the treatment referred to, which. cause it to the her and sulfur constituent of the stock lose an undue proportion of the gums and oils under treatment. forming componentparts of caoutchouc,and If it is desired to recover'rubber having the tender y to eterioration is mainly such fillers as lead, zinc, and lime removed 9o 5 caused b the detrimental action on the rubfrom it, I employ hydrochloric acid, and if ber of so uble salts and other foreign matter the removal of fillers is not desired I employ dissolved by the chemicals emplo ed in the sulfuric acid, the time of treatment being the treatment and which thefinalwaslling of the same with either acid, though a solution of product fails to remove because of insufii; the strength of fifteen to twenty er cent. 5

o cient thoroughness in the washing operation, produces the best results when by rochloric absolute thoroughness therein being so difliacid is used. v,

; cult as, to be impracticable of accomplish- By mixing and boiling with the rubber ment, owing to the spongy quality of the waste in a finely-divided condition the solufinal product. tion of salted acid the action on the heaviest I00 The general object of my invention is to cotton fiber so disintegrates itwlthin apeproduce reclaimed rubber of superior quality riod of about five minutes as to adapt It to be due to its freedom from the undesirable charreadily icked to blts, and Within a period of acteristics referred to, and this I successabout t irtIy minutes the rubber begins to fully accomplish by employing for treatment swell and-b ossom, this action contmu ng for m 5 of the waste materialweak chemical solua'period of from fifteen to forty-five minutes,

' tions under ordinary boiling temperatures, depending upon the strength of theacid soluby rendering the total period of time for sub tion and the amount of salt used The rub,-

jecting the rubber to contact with chemicals ber is then removed and pressed or squeezed about two hours, by resupplying t0 the rubto drain out of it the liaprid and is swollen by 1 1o 5 5 her any gums lostfrom it by solution, by inthe treatment to fully ee times its original corporatmg in the recovered rubber a prebulk. Moreover, the, treatment has reduced it to a condition of thorough devulcanization and to a light-gray color, which darkens somewhat in the subsequent step of drying the rubber. Most of the liber remains in an undissolved state and precipitates in the solution fromwhich it may be readily removed, as by screening. Pouring the mass over a tortyanesh screen will remove all or practically all o fltlie disintegrated iiber, while the particles of rubber are so swollen as to be intercepted by'the screen and saved. The rubber product is then thoroughly washed with clean water or first subjected to an acid-neutralizing treatment with a suitable alkali, such as soda or the like, and thereupon dried. It used in this state, as it may be, the color of the rubber when the latter is rolled into a sheet will be a medium shade of gray, if hydrochloric acid was used in the treatment, and a somewhat darker color it the chemical used was sulfuric acid. The rubber product of the described treatment, however, is deficient in the degree of gumminess and tackiness desirable for it to possess for utilization.

To impart to it these qualities, I apply my discovery that rubber will take up a resin from such solutions as resinatc of sodaor resinous borate of soda by boiling the product ol' the iirst-described treatment for a period of about thirty minutes (though the boiling period may be prolonged without detriment to the product) in a weak solution of either or both of these solvents, the duplex solution being, however, preferred, owing to the well-known preservative eli'ect on vegetable matter of boracic acid and alkaline borates. 1 find that superior results are produced where for each pound of the rubber atw'o-per-cent. soda solution is used, to

which one-fourth oi an ounce of soluble gum,

such as common pine-tree rosin or shellac, and one-fourth of an ounce of borax or oneeighth of an ounce'of boracic acid have been added; but it is not essential to use both gum solvents, either one used alone atl'ords a very good product. As the next step in the treatment the rubber is subjected to thorough washing, but it is found to be practicallv impossible to removetrom it all the soluble matter as perfectly as is desirable toinsure to it the quality of durability. I therefore drain oil the gum solution and boil the rubber for a period of about fifteen minutes in water to which a suitable precipitant (preferably an aluminium salt, such as alum) is added in sullicient quantity (say about one-half of an ounce to each gallon of water) torender insoluble and precipitate the solu ble matter, with the result. of thoroughly clarifying the solution. This treatment has the l'urther peculiar action ol causing con siderable ol' the sand and other impurities, which have resisted all the other treatments referred to which are known to me, to drop out 01' the sponge-like rubber product.

The rubber thus recovered is washed and dried and whenreduccd to sheet form possesses every charaoterist-ic of the virgin article compounded-namely, that of presenting a glossy edge, when cut, toughness, and elasticity in a degree fully fifty per cent. greater than any rubber I have been able to reclaim by any of the treatments in use at the present time, and my product is free from fiber and has excellent working and keeping qualities.

1 have ascertained that calcium chlorid acts almost as energetically as sodium chlorid in applying it to my purpose as a substitute for the common salt, also that potassium chlorid is effective and that the simple salts of the other halogen elements, such as the iodid or bromid of potassium or sodium may also be used, my purpose in mentioning these substances being to suggest that my investigations have included them, and find their action to be peculiar. Thus, for example, by adding potassium iodid to a tenper-cent. solution of sulfuric .acid containing cotton fiber the liquid remains yellow while boiling during the period of about fifteen minutes, in which the fiber is undergoing decomposition without disintegration; but the instant that disintegration of the fiber takes place a strong reducing action shows itself and theiodine is set free from the solution, which becomes of a deepviolet color;

My improvement pertaining to the use of a suitable salt by adding it to the weak acid solution is not to be confounded with a patented process known to me for recovering rubber from rubber waste, in which hypochlorid of lime in an acid solution or a mineral acid with salt and an oxidizing agent, such as peroxid of manganese, are employed, for these would not subserve my purpose, since the chlorin of these salts and mixtures are convertedinto gaseous chlorin and escape as such, while the gist of my decomposing solution is the presence of a simple chlorid salt of an alkaline element which does not set free its chlorin in the presence of a mineral acid. In the practice of my improvement addition of ahypochlorid would be a mere waste and mterpose a nuisance n working,

though suchaddition would be within my invention it made to an acid "solution containing a simple chlorid salt in such quantity that its chlorin is-not practically aliset free in the gaseous state. I

that I claim as new, and desire to secure by Letters Patent, is-

1. The process of recovering rubber from rubber waste, which consists in boiling the finely-divided material in a mineral-acid solution with the addition of a halogen salt of the alkaline group, such as sodium or calcium chlorid, without setting free .in a gaseous state the chlorin, bromin, or iodin, and removing the dissolved and decomposedfiber.

ITO

2. The process of recovering, rubber from rubber waste, which consists is; boiling the iinelysdivided material in a mineral-acid solution with the addition of a haiogen salt of the alkaline group, such as sodium or calcium chlorid without setting free in a gaseous state the chlorin, bromin or iodin, and removing the dissolved and decomposed fiber and mineral substances.

3. The process of recovering rubber from rubber waste, which consists in boiling the finely-divided material in a mineral-acid solution with the addition of a halogen salt of the alkaline group, without setting free in a gaseous state the chlorin, bromin or iodin, removing the acid and dissolved matter from the rubber, then boiling the rubber in a solution of alkaline salt, and washing and drying the product.

4-. The process of recovering rubber from rubber waste, which consists in first decomposing and then removing the fiber, and treating the resultant rubber product with solution of an alkaline salt, such as soda or potash, with the addition of a chemical substance having a preservative effect on vegetable matter, such as boracic acid or sodium borate, and washing and drying the product.

The process of recovering rubber from rubber waste, which consists in first decomposing and. then removing the fiber, and treating the resultant rubber product with a solution of an alkaline salt, such soda or potash, with the addition of a soluble gum, and washing and drying ti e p oduct.

(i. ihe process of recovering I berirom rubber waste, which consists 1n 1 posing and then removing the fiber, and treating the resultant rubber product with a solution of alkaline salt, such as or potash, with the addition of a chemical substance having-a preservative eiiect on vegetable matter, such as boracic acid or sodium borate, and of a solubie guru, such rosin or shellac, and washing and drying the product.

7. As step in the recovery of rubber from rubber waste by decomposing and separating the fiber from the rubber by subjecting the material to the action of suitable chemical solution, that of removing from the rubber product solo." compounds remaining from the solution employed in previous treatment, which consists in rendering said soluble compounds insoluble and removing them from the rubber product by precipitation.

8. As a step in the recovery of rubber from rubber waste by decomposing and separating the fiber from the rubber by subjecting the material to the action of a suitable chemical solution, that of removing from the rubber proddct soluble compounds remaining from the solution employet'i in previous treatine t, which consists in rendering insoluble and precipitating said compounds by treating said produc- 'ith a weak astringent solution of aluminium sal t.

The process of recovering rubber from rubber Waste which consists in boiling the materiel in a finely-divided state in a mineral-acid solution with the addition of a halogen salt, removing the dissolved fiber, boiling the rubber product in a solution 01: an alkaline salt, with the addition of a chem lcal substance having a preservative effect on vegetable matter and with a solubie gum,

tringent solution of an aluminium salt havmg the eiiect of rendering insoluble. any reinannng soluble coinpoumls in. the rubber and precipita tin the same, and finally washing and drying the product.

"ii' ILLiAli-l A. llJii lhihil.

In presence of L. rinrsms, J, H. LAUDEuS.

then treating the product with sneak as- 

